MAYPORT NAVAL STATION, Fla. » A Navy sailor pleaded guilty Tuesday to secretly videotaping female trainees as they undressed for showers aboard a submarine, becoming the fourth crew member of the USS Wyoming to be sentenced to prison in a case that has tarnished the U.S. military’s integration of women into its submarine fleet.

A court-martial sentenced Petty Officer 3rd Class Cody Shoemaker to 18 months in prison and a bad-conduct discharge. The 22-year-old missile technician told a military judge that twice last spring he used a cellphone to record female midshipmen from a tight crawlspace that looked into the shower area from beneath a sink.

"The Navy has brought women into the submarine force and the accused has not gotten onboard," Lt. Cmdr. Lee Marsh, a Navy prosecutor, said in asking the judge to "send a message to that submarine force that all sailors, male and female, will be treated with dignity and respect."

In addition to midshipmen — students from the U.S. Naval Academy or college Navy ROTC programs — prosecutors say four female officers serving on the Wyoming were also recorded undressing and sailors traded the videos "like Pokemon" cards for energy drinks and other items.

Three other sailors pleaded guilty in the case last week and three more are still awaiting trial. The stiffest sentence so far has gone to Petty Officer 2nd Class Charles Greaves, who pleaded guilty to recording the female officers. He received two years in prison and a dishonorable discharge.

"That feels significant, but not out of the range I would expect to see," said Victor Hansen, a former military prosecutor and defense attorney who’s now a professor at the New England School of Law.

With all defendants who have pleaded guilty so far sentenced to jail time, Hansen said, the Navy seemed to be saying "if you’re involved at any level, this is going to be more than a slap on the wrist."

Last Wednesday, Petty Officer 2nd Class Joseph A. Bradley pleaded guilty to sharing videos of the officers and received 30 days confinement and a reduction in rank. Petty Officer 3rd Class Brandon McGarity, whose crime was failing to report the videos to superiors, got 15 days confinement and a reduction in rank after he pleaded guilty Friday.

No female trainees were called to testify against 22-year-old Shoemaker. Marsh said the sailor’s victims were recorded "from the waist down" and couldn’t be identified on the videos.

"I offer the most sincere apologies to the female midshipmen," Shoemaker told the judge. "I know that I have potentially swayed their decisions to become female officers on submarines."

The four female officers who were recorded by another sailor have said the videos either ruined or harmed their careers.

The charges to which Shoemaker pleaded guilty carry a maximum penalty of six years in prison, and prosecutors asked the judge to impose a three-year sentence. Shoemaker’s defense attorney, Lt. Jennifer Buyske, told the judge he deserved no more than six months behind bars and noted he has a wife and two young children.

"You don’t have a predator on your hands," Buyske said. "You have a young man who made terrible decisions."